print(type({1, 2}))

skills = set()

# pass an iterable to set()

skills = set(['Problem solving', 'Critical Thinking'])

characters = set('letter')
print(characters)
print(len(characters))

if 't' in characters:
    pass

characters.add('s')

if 's' in characters:
    characters.remove('s')

characters.discard('s') # doesn't raise an exception

print(characters.pop()) # uncertain

# frozen a set

chars = frozenset(characters)